The present invention relates to debugging and testing equipment for use in the development of microcomputers.
In developing a modern microcomputer a prototype motherboard is first constructed, which must then be debugged through the use of the specialized microcomputer debug tools. In so doing, error related to the electronic circuit elements and/or the system will be detected and corrected early, before substantial costs are incurred.
The most extensively used microcomputer debug tool is known as an In-Circuit Emulator--ICE. This type of debug tool has a CPU which is the same as the CPU used on the prototype motherboard to be debugged, as well as other elements and circuits. In the testing arrangement, the ICE is connected with the microcomputer motherboard through one buffer and with a host testing computer through another buffer. During the testing procedure, the CPU of the ICE simulates the operation of the CPU on the motherboard and processes all the testing steps.
During the simulation testing procedures, the timing of the system clock signals is delayed and signal quality is affected because of the presence of the buffers and the influence of the data transmissions. Unfortunately this prevents the actual working speed from being simulated. In the infancy of microcomputer development, when speeds were slow and only a few microprocessors were available, the influence of the delayed system timing caused by the ICE did not constitute a significant difference when compared with the system timing in a real-time environment. However, at the present time, more microcomputer systems employ high system speeds, for example 12 megaHertz (mHz), 16 mHz, or even beyond 20 mHz. In addition, many different microprocessors have their own bus and control status. If an ICE is used for the debug tool, then an ICE must be chosen which corresponds closely to the CPU and speed which the motherboard employs. Unfortunately, because of the timing delays, there will be a significant difference between the simulated environment and the real-time ennvironment when the motherboard employs a higher system speed. Due to this difference the real-time working status, when the motherboard is running at very high system speed, will differ at least partially from the simulated testing status, when the motherboard is running under the debug environment using the ICE. These are the main drawbacks of the In-Circuit Emulator, which, additionally, has a highly complicated design.